In 1935, Einstein, Podolsky, Rosen (EPR) used their famous criteria of realism and locality to conclude that the wave function does not provide a complete description of physical reality. Their argument (adapted to Bohm's gedanken experiment for a pair of photons in the singlet state) is based on the following three premises:
1 - Quantum mechanical (QM) perfect correlations: If the polarization of photons 1 and 2 are measured along the same axis, then the outcomes are perfectly (anti) correlated.
2- EPR's criterion of realism: "If without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity, then there exists an element of physical reality corresponding to this physical quantity."
3 - Einstein's locality: "But on one supposition, we should, in my opinion absolutely hold fast: The real factual situation of the system S2 is independent of what is done with the system S1 which is spatially separated from the former."